Amyotrophic Lateral SclerosisAmyotrophic lateral sclerosis (ALS) is a disease of the motor nervous system where nerve cells die in the brain and spinal cord that are responsible for the human locomotor system ("motor neurons").
The causes of ALS are unknown.
During the early phase the disease of motor neurons leads to frequent involuntary movements of individual muscle groups ("fasciculations") and cramps. In the further course usually the affected muscles recede ("muscular atrophy") since they are no longer in use after separation from the control unit (similar to the atrophy of muscles while wearing a cast).
Amyotrophic lateral sclerosis is considered incurable. Death often occurs from respiratory paralysis or inflammation of the weakened lungs. Since death is not caused by lack of oxygen but an oversaturation of carbon dioxide, suffering people fall asleep peacefully.
The average survival time is about 3 years after diagnosis. The course of ALS is not predictable. Much longer survival times are possible, as proven by the famous astrophysicist Stephen Hawking, diagnosed with ALS in 1963. Approximately one in 20 patients with this disease will survive 10 years or longer.
Different Names - One Disease"Amyotrophia" is understood by the physicians with muscle wasting. "Lateral" means parts of the body facing away from the center, e.g. arms and legs. Sclerosis is a hardening of an organ.
Once in German the disease was also known as "Myatrophe Lateralsklerose". Under the influence of naming in the United States, however, the term ALS also prevailed in Germany. In Britain it is still called MND (motor neuron disease). Though this term rather denotes a generic term of motor neuron diseases, which includes not only ALS.
Jean-Martin Charcot, a French physician, specified ALS as early as 1880 and distinguished it from other neurological diseases, so that in Europe it was first known under the name "Charcot's disease". In the USA, ALS was initially known as "Lou Gehrig's disease", named after an American football player of German descent who suffered from ALS in 1938.
The motor nervous system and ALSThe motor nervous system includes the first motor neuron (central motor neuron, upper motor neuron) and the second motor neuron (peripheral motor neuron, lower motor neuron).
The first motor neuron can be found in the brain and sends control commands to the spinal cord, where they are received by the second motor neuron and transmitted to the respective muscle.
Amyotrophic lateral sclerosis causes damage in both motor neurons:
Disease of the first motor neuron (from cortex to spinal cord) leads to muscle weakness (paralysis, paresis) and additionally becomes noticeable by an increase in muscle tension ("muscular tone"). This increase of tonus in a spastic manner leads to muscle tremor ("fasciculation") and muscle cramps ("clonus") caused by spontaneous firing of the motor unit ("anterior horn cell"). While firing, the respective anterior horn cell is still alive and the muscle is still moving, which counteracts the muscle wasting.
The disease of the second motor neurons (spinal cord to muscle fiber) leads to progressive paralysis of the respective muscle group as well as lowering of tonus.
Therefore the result is a mixed picture of symptoms which are partially contradictory.
The lowering of tonus occurs frequently, and gains the upper hand in the further course of the disease. In general, the cortical areas for the control of face, tongue, hands and legs are affected sooner and more intensely than other areas.
Symptoms and DiagnosisIt is estimated that the disease's symptoms are visible only 10 years after onset. A diagnosis is made by exclusion of similar diseases.
Amyotrophic lateral sclerosis is not primarily a disease of the muscle itself ("muscular dystrophy"), but an atrophy caused by the muscles lack of use. The so-called CK, which can measure the standard deviations of the enzyme "creatine kinase", which is mostly found in muscles being important for the energy supply of cells, shows at most minimally increased levels.
Furthermore, ALS is not a disease of nerve conduction, but only of the anterior horn cells. Therefore the measuring of nerve conduction usually yields values within the normal limits.
The sense organs such as sense of vision, hearing, taste and smell are not affected. Likewise with the so-called "smooth muscle", i.e. those muscles that are not controlled voluntarily (gut, sphincters, bladder), etc.
Actual affected is the bulbar system as well as the first and second motor neuron. This results in speech and swallowing disorders, increased muscle tension, myasthenia (muscle weakness), muscle wasting, fasciculations and muscle cramps.
To exclude other sources of the symptoms such as multiple sclerosis or meningitis usually a magnetic resonance imaging (MRI) and a cerebrospinal fluid examination is performed.
The spontaneous firing (fasciculations) can, unless they are obvious anyway, be detected by electromyography (EMG).
Frequency increases with age and in old age decreases again. Men are affected slightly more often than women. In a few cases (5%-10%) ALS occurs within the family (then even at an earlier age).
Cause of the diseaseMeanwhile, it was found that the damage is induced by cellular waste (protein inclusions), deposited in the motor neurons. The cause is still unclear. There is a consensus among some physicians that an overload of the locomotor system, e.g. in athletes, promotes the development of the disease.
There is no prove whether overstraining, inflammation or a virus could lead to the premature aging of the locomotor system. A virus is considered unlikely.
Course of the diseaseThe disease often begins with weakness in the hand or forearm as well as sometimes in the legs or the muscles of the vocal apparatus. Almost always, paralysis or muscle flutter appear on one side (asymmetric).
The disease proceeds continuously. That means there are no relapses as with other diseases (e.g. multiple sclerosis), so that the sufferer can better adapt to the new situation. Neither intelligence nor language comprehension have ever been affected by the disease. So sufferers experience the disintegration of their own body with full consciousness ("a prisoner in the body").
The (primarily asymmetric) muscle wasting becomes visible by and by.
Initial spasticity often disappears in the further course, once the disease of the peripheral system gains the upper hand.
Therapy and aidsThere are attempts to counteract the progression of the disease with medication. Here, it is essential to begin treatment as early as possible. Moreover, the therapy is limited to symptom management and maintenance of the independence (autonomy) by appropriate means.
At least, occupational therapy or physiotherapy can counter restrictions on movement as well as speech therapy can control swallowing disorders.
By means of tools such as wheelchairs or gripping pliers, the independence of the person concerned will be maintained for some time.
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